The first Gryffindor Quidditch practice of the season has been cut back
drastically; Oliver isn't shown wasting practice time lecturing
the team before heading to the pitch.

Instead of asking questions about the Chamber in History of Magic,
Hermione does so in Transfiguration.

Snape's line about sending someone home in a matchbox from the Duelling
Club is no longer in reference to Justin Finch-Fletchley if paired with Neville,
but about Harry if paired with Ron (given Ron's malfunctioning wand).

Malfoy's first spell at the Duelling Club has been changed to
"Everte Statum".

Switching Spells

Arthur Weasley asks Harry about escalators in the book, but rubber ducks
in the film.

Hermione gets Dumbledore's line, "Fear of a name only increases
fear of the thing itself,"
(PS17) in the film.

Second-year Gryffindors have Herbology with the Hufflepuffs in the
book, but with the Slytherins in the film.

Hermione also gets the bulk of Ron's lines in Hagrid's hut, describing
the significance of the word "Mudblood."

Again, Hermione gets a line of Ron's when she says that "even in
the wizarding world," hearing voices isn't good.

McGonagall tells the students about the Chamber in the film,
instead of Professor Binns, who has yet to make
a real appearance in the films.

In the book, the statue of Slytherin represents him standing,
while in the film only his head and shoulders are represented.

In the book, after Fawkes injures the basilisk's eyes, Tom Riddle tells
the serpent he can still "smell him". In the film, Tom
instructs the serpent that he can still "hear him," resulting
in the invention of a scene in the film involving Harry throwing a rock
to mislead the basilisk.

In fact, snakes do not have external ears and are pretty much
unaware of airborne sound as a result. However, they are sensitive
to vibration, so perhaps the basilisk is intended to have felt the
vibration in the tunnel floor when the rock hit it.

In the book, Fawkes saves Harry from the basilisk venom before
Harry destroys the diary. In the film, Harry is not healed by
Fawkes' tears until after the destruction of the diary and
Ginny's awakening.

In the book, Harry's conversation with Dumbledore after the defeat
of the basilisk takes place in McGonagall's office, and Arthur,
Molly, and McGonagall are present at the start of the scene. In the
film, the scene is set in Dumbledore's office instead, and
McGonagall and Ginny's parents do not appear.